Late onset cone dystrophy.

Cone dystrophies are a hereditary, progressive and heterogeneous group of retinal diseases with cone system degeneration. They lead to reduced visual acuity, colour vision impairment and photophobia. Full-field electroretinogram (ERG) reveals severe cone function impairment, with normal rod responses or slightly depressed in advanced stages in some cases. The purpose of the study was to present a case of late onset cone dystrophy in 47-year-old male and the proper diagnostic procedure. A 47-year-old patient presented with progressive visual loss for several years and mild photophobia, which he observed recently. The patient underwent fundus photography, fluorescein angiography, colour vision testing, Goldmann visual field testing, full-field electroretinogram (ERG) and multifocal electroretinogram (mfERG). Symptoms and signs of late onset cone dystrophy may be unclear and establishing the proper diagnosis may be difficult in these cases. Patients may be misdiagnosed as having other diseases, especially in case of absence or subtle changes in the macula. The electrophysiological testing is essential in these cases, and ERG is the most useful clinical test in early and differential diagnosis of retinal dystrophies.